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Finding multiple sun-earth saddle-point flybys for LISA Pathfinder

Fabacher, Emilien Finding multiple sun-earth saddle-point flybys for LISA Pathfinder. (2013) In: International Astronautical Congress (IAC2013), 23 September 2013 - 2013 (Beijing, China).

(Document in English)

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More than 70 years after its existence was postulated for the first time in order to explain the observed rotation curves of galaxies1, the nature of Dark Matter remains a complete mystery. After several decades of research, no particles have been detected to support this theory. Thus, other theories have been developed to explain Dark Matter problem. Rather than postulating the existence of a new matter, they tend to explain the observations by modifying the gravitational laws. TeVeS and its non-relativistic limit MOND2 is one of these theories. To date, proof to confirm it has not been provided either, but could be in a near future, thanks to ESA mission LISA Pathfinder. LISA Pathfinder is a mission due to be launched in the next few years. It carries on-board an extremely sensitive gradiometer which would be able to measure deviations from Newtonian gravity, hence demonstrating MOND theory. Doing so, however, requires that LISA Pathfinder spacecraft reaches a specific point in the solar system, called the Sun-Earth Saddle Point (SP). The SP is the point located between the Sun and the Earth where the gravity of the Sun exactly equals the gravity of the Earth. This point is very singular because of its very low gravity gradient, which recent studies have demonstrated would make MONDian effects measurable3. However, LISA Pathfinder spacecraft is to be injected in a halo orbit around the first Sun-Earth Lagrangian point (L1), at more than one million kilometres from the Saddle Point. Therefore, it has been suggested to fly the satellite by the SP in an extension to its nominal mission. The challenge issued by this additional trajectory lies in the ΔV budget. While a total ΔV of approximately 3 km/s will be used to reach L1 from a LEO orbit, a budget of only 4 to 5 m/s is supposed to be remaining at the end of the nominal mission. Despite this harsh constraint, this study shows that reaching the SP from a given L1 halo orbit is feasible. Furthermore, as it has been emphasized that flying by the SP more than once would be very profitable for the experiment’s reliability, trajectories reaching twice the SP have been created. Nevertheless, these trajectories have not been designed as coming from a given halo orbit around L1, as it would be necessary once the exact orbit known during the nominal mission. On the contrary the solutions found, although respecting the specifications on LISA Pathfinder mission trajectory, are not independent of the halo orbit part of the trajectory. Until now, it has not been possible to find orbits reaching twice the SP from a given halo orbit. Therefore, the final aim of this study is to assess the possibility of designing a trajectory flying twice by the Sun-Earth SP, once the actual orbit of LISA Pathfinder spacecraft is known. To do so, orbits like the ones designed by ESA/ESOC for the nominal mission are used. Conditions under which such double SP flybys could happen are evaluated, and methods to design interesting orbits are defined.

Item Type:Conference or Workshop Item (Paper)
Additional Information:ISBN : 9781629939094, éditeur : International Astronautical Federation (IAF)
Audience (conference):International conference proceedings
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Institution:Université de Toulouse > Institut Supérieur de l'Aéronautique et de l'Espace - ISAE-SUPAERO (FRANCE)
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Deposited On:30 Jan 2015 10:24

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